I have a SITE, and a SHIPTYPE table. These two table have a many-to-may relationship (the cross reference table is SHIPTYPE_X_SITE). I created the corresponding entities Site and ShipType. For the creation of ShipType, my UI has ShipType related fields as well as a list of sites. Therefore,ShipType has a collection of Sites:

Once I did that, if I modify Site and save (collection shipTypes is null), all the cross reference records are gone for the given site. My question is how can I make the Site bean has the association, but not doing the cascading? Thank you very much for you help.